An automatic assembling system and method for camera lens units are provided. The system includes a main workstation, a barrel-feeding station, a lens-feeding station, and a camera lens-removing station. The method includes (A) operating a plurality of barrel-clamping units of the main workstation cyclically and intermittently along a feeding direction; (B) moving a plurality of barrels from a barrel standby area of the barrel-feeding station onto the barrel-clamping units in sequence; (C) moving a plurality of lens units from a lens standby area assembly of the lens-feeding station into the barrels to form the camera lens units; and (D) moving the camera lens units from the barrel-clamping units into a camera lens-collecting area of the camera lens-removing station. The steps (B, C, D) are performed in cooperation with the intermittent operations of the barrel-clamping units.